This invention relates generally to rail vehicle inspection systems.
Known rail vehicle inspection systems include transducers mounted to rails. Typically, at least two transducers are longitudinally spaced apart from one another along the rails. The transducers may each be referred to as a wheel gate. The space between the transducers may be referred to as an inspection window. When a rail vehicle such as a train passes through the wheel gate, the transducers determine when the wheels of the rail vehicle enter and exit the inspection window. The transducers determine when wheels are in the gate to permit detection systems to inspect the axles of the rail vehicle; to count the number of axles in the vehicle, to determine a speed of the vehicle, and the like. For example, in hot box detection systems, the transducers identify when wheels enter the inspection window, or heat detection window, so that the system can measure the thermal profiles of corresponding axle bearings. Some known transducers use a permanent magnet that provides a magnetic field. As wheels pass through the field, the wheels cause magnetic flux to vary, which induces an electric current in a coil of the transducer. The induced current is used to identify movement of the wheel relative to the transducers and into and out of the inspection window. The waveform of a signal representative of the current induced in the coil typically has a predominantly positive polarity and resembles a sine wave when a wheel/has passed the transducer. The waveform may be monitored to determine when the signal increases to a positive peak value and then falls below zero to determine when a zero crossing occurs. The occurrence of a zero crossing indicates that the wheel is located or centered over the transducer.
The transducers in known inspection systems may be incorrectly installed or wired. The terminals, leads or wires of a transducer may be inadvertently switched by operators who install the transducer. For example, the positive and negative wires of the transducer may be switched. The switched terminals may cause the waveform of the transducer signals to have a predominantly negative polarity and resemble cosine wave. The negative polarity signals may not accurately reflect the movement of wheels with respect to the transducer. For example, in contrast to the waveform of a positive polarity signal, the negative polarity waveform does not increase to a peak positive value or fall to a zero crossing. Additionally, the increase of the negative polarity waveform upward toward zero may be incorrectly identified as a wheel approaching the transducer. As a result, an incorrectly wired or installed transducer may be unable to accurately identify the location of a wheel relative to a transducer and the entry or exit of a wheel into the inspection window. Incorrect identifications of wheels entering and exiting into wheel gates may result in inaccurate axle counts or missed hot boxes, for example.
Thus, a need exists for a method and system to correct for signals obtained from incorrectly or improperly installed transducers. Such systems and method may improve accuracy in identifying when a wheel of a rail vehicle enters and exits a wheel gate, thereby providing more accurate inspections of axles, counts of axles in a rail vehicle, and the like.